The present invention relates in general to a cotton gin, and more particularly to a roller cotton gin constructed to strip lint from the seed of seed cotton with a high degree of efficiency and having high capacity.
The ginning of cotton, which is the operation in which the seeds are separated from the cotton fibers, is customarily carried out either in a saw gin or in a roller gin. The saw gin has been the dominant type for ginning the fuzzy seed Upland Cotton while the saw gin has not been acceptable for use on the Black Seed Cotton which generally has a longer staple. When ginning the extra long staple Black Seed Cottons, which are commonly referred to as a variation of Egyptian Cottons, on saw gins fiber breakage results in a shorter staple and generally a less desirable fiber for the high-quality products for which this fiber is normally used.
To generally distinguish between these two basic types of cotton, by far the most common type of cotton is the Upland Cotton which varies in staple length from less than 3/4 inch to more than 11/8 inch. The seeds are fuzzy and each fiber is almost always saw ginned, although there are periodic efforts to roller gin the longer staple varieties to better preserve the fiber quality.
The other type of cotton is sometimes referred to as Black Seed Cotton, but more commonly referred to as extra long staple cotton. The staple length of this cotton varies widely as with the Upland Cotton but the more common varieties are about 13/8 inch to 11/2 inch in staple length. The fibers are very fine and silky and can be used in very expensive materials. Saw gins break and tangle these fine fibers which lowers their quality. Also, the fibers are so gently attached to the slick surface of the seed, the performance of the saw gin is not very satisfactory. For these reasons, this black seed cotton is almost always roller ginned.
A particular disadvantage has been encountered heretofore in connection with roller gins in that, whereas a saw gin produces fibers continuously, roller gins heretofore used are somewhat intermittent in operation. This occurs because of the fact that there is a reciprocating blade employed that cooperates with the ginning roller and a stationary doctor knife to strip the seeds from the fibers as the fibers are drawn past the doctor knife by the ginning roller. The reciprocation of the moving blade serves to interrupt the flow of cotton to the ginning roller so that in this type of roller gin, the productive rate of the roller gin has been relatively slow. The high quality of the fibers produced by a roller gin, however, have caused it to continue in use, particularly in regions where the cotton is characterized by particularly long fibers.
Various attempts have been made to improve the roller cotton gin and, in particular, to improve the gin with respect to the rate of fiber production in order to reduce the cost of ginning the Black Seed Cotton, while at the same time retaining the advantageous characteristics of the roller gin that the fibers produced are not entangled or broken.
Much effort has been given to alleviating difficulties with the length of time required in roller gins to pull the fibers from the seed, particularly long fibers, and to dislodge the seed from the fibers with the seeds in a relatively fiber-free condition, and do this continuously at a relatively high rate of speed. This has led to the construction of a roller gin having a ginning roller turning against a stationary knife so that the fibers will be drawn under the knife while the seeds are retained, and utilizing with this construction rotary or continuously moving knife means to knock the seeds away from the stationary knife. Difficulties have been encountered however in producing clean seeds with this construction because not enough ginning time was given to pull the fibers off the seeds and some considerable seed cracking occurred.
In the case of roller gins employing a reciprocating blade for the purpose of dislodging the seeds from the stationary knife, it has been proposed to have the moving blade overlap the stationary knife by about 1/2 the length of the staple of the cotton being ginned. Fibers are pulled, by friction of the ginning roller, under the knife until the seed is against the knife edge. The friction is not always great enough to pull all the fibers from the seed, in which case it is necessary for the blade to push the seed away from the knife edge. In the case of the reciprocating blade, it operates parallel and close to the top surface of the blade to push the seed away. If the seed is not pushed beyond the length of most of the fibers, the friction on the fibers still held between the roller and the knife will draw the seed back to the knife, at which time most if not all the fibers are removed. It is difficult to determine accurately how many times an individual seed returns before all fibers are removed, as this depends on a number of variables, the most obvious one being the pressure of the ginning roller against the knife. The pressure can be enough for the friction to remove practically all the fibers as the seeds are pushed away by the blade. However, such pressure will usually cause the roll to overheat.
The overlap of the reciprocating blade of approximately one half the staple length has been accepted by those experienced in ginning extra long staple cottons for many years. The fact that the reciprocating blade completely blocks the access of the cotton to the ginning roller during its travel across the knife limits the capacity of such a method drastically. The economics of this method limits its use to the very longest staple of high quality whose value would be greatly reduced by saw ginning.
Literally hundreds of roller ginning machines have been designed in an effort to increase the capacity and thus reduce the cost of roller ginning. In spite of these efforts the reciprocating blade method prevailed through the 1950's. Subsequently, as a result of work by some engineers engaged in a program to improve methods of roller ginning at the U.S. Department of Agriculture's Ginning Laboratory at Mesilla Park, N.M., there appeared in about 1961 a roller gin design using square bars mounted on a driven chain system to travel over a knife, allowing the cotton to be fed to the ginning roller between the bars. This was called "the flight bar gin". Several companies manufactured and installed elaborate and expensive plants using the flight bar gin principle, but these plants were not successful, because it was not possible to maintain the required pressure on the flight bars as they moved over the knife, since sprocket and chain wear necessitated constant adjustment.
In analyzing the difficulties encountered with the flight bar gin and studying the art, I concluded that a rotating blade would serve the same purpose as the flight bar or the old reciprocating bar and permit attainment of improved roller ginning. Study of the art showed that rotating blades, such as blades on a rotating cylinder, had been previously tried and found to be unsuccessful, but the rotating cylinders with blades in those cases were approximately the diameter of the ginning roller which allowed for an overlap much greater than the staple length. I determined that many of the problems previously encountered with such large diameter rotating blades or with the flight bars should be alleviated by using a rotating blade about 23/4 inches in diameter and an overlap with the knife of about 3/4 inch and a number of roller gins having this dimensional relationship and arrangement have been previously used for cottons having a staple length of, for example, about 13/8 inch to 11/2 inch.
I have devoted considerable study to investigation of the optimum diameter, speed and configuration of the rotating blade device and the overlap, particularly with regard to roller ginning of the shorter staple cotton. My studies indicate that for Upland Cotton the blade device should be about 2 inches in diameter to achieve optimum release of the seed after about 1/2 inch to 5/8 inch movement. In considering the configuration to maintain the required rigidity with such a small diameter blade and the number of blades to be provided, the R.P.M. is a factor. A study of the relationship of the surface speed of the rotating blade to that of the ginning roller indicates that the ratio should approach 1:1. If the ginning roller, as it approaches the ginning point, is fully covered with cotton, and the surface speed of the rotating blade is significantly less than that of the ginning roller, there would be intermittent build-ups of cotton ahead of the rotating blade as each blade comes into ginning position. These build-ups overload the ginning capacity of the ginning roller intermittently, resulting in the necessity to cut back the feed. The build-ups can be eliminated by setting up the surface speeds of the ginning roller and rotating blade to be close to the same speed.
With this established, the question of the number of blades on the rotating blade assembly can be determined within reasonable limits. As the seed is pushed away from the ginning point to the release position it must have time to return to the ginning point before the next blade moves to the ginning point. The travel of the ginning roller surface must be enough to pull the seed back to the knife before the next blade reaches the knife edge.
It has been determined that a rotating blade assembly in the range of 2 inches in diameter for Upland Cotton and in the range of 3 inches in diameter for extra long staple small seed cotton, and having four blade points or blade members more nearly meet this criteria. Of course, if more than four blades are used on the rotating blade assembly, the speed of the rotating blades has to be reduced or the speed of the ginning roller increased to avoid having the blade hit the seed before it returns to the knife edge, thus leaving lint on the seed.
It has been discovered, however, that a roller gin construction involving a rotatable blade assembly of such small diameter with straight blades, when the gin is operating at higher capacity, results in vibration, chattering and bumping of the rotobar forming the rotating blade assembly due to build-up of seed and fiber against the knife edges of the rotobar in the interval between the passing of the rotating blades over the knife edge, and having the straight edge strike them at the same instant along the length of the rotobar. This load is sufficient to cause the rotobar to flex, a condition which causes unginned seed locks to pass under the rotobar or rotating blade assembly with the seed.
This problem is eliminated by arranging the blades in a spiral fashion and forming them as radical blade members provided in a spiral groove on a cylindrical shaft, with the blades executing a spiral turn of one turn per length across the length of the blades on the rotating blade assembly. In one example, this may span a width of about 481/2 inches, so that the spiral blades, four of which are provided, will execute one turn across the total length of the 481/2 inches. It was found that with such a rotobar construction using spiral blades, the capacity can be increased to the extent that the cavities or channel-like pockets between the blades are sufficiently filled with unginned seed locks that the mass of seed lock in the pockets push the fibers down to the pinch point in a manner producing very advantageous operation.
When a few fibers from a seed lock or a group of seed locks are caught in the pinch point, between the knife edge and the ginning surface, adjacent and continuous fibers have enough attractive force to pull the entire group of fibers into the pinch point. A typical surface speed for the ginning roller is about 100 inches per second so the time element for the ginning of a single seed lock is very limited and of course conditions have to be ideal for the fibers to be caught in the pinch point as they move over it at this speed.
A spiral rotobar as described above, having a plurality of spiral blades executing one turn along the length of the blade portion of the rotobar, will permit the seed to be released by the blade after a travel of about 1/2 the staple length from the pinch point. One arrangement found to be satisfactory for extra long staple cotton is a ginning roller diameter of about 15 inches diameter, and a stationary knife blade mounted at approximately a tangent to the point of contact, and a rotating blade assembly of about 3 inch overall diameter located with its center line in the radial plane of the ginning roller which passes through the point of contact of the blade with the ginning roller, and with the blades clearing both the ginning roller surface and the blade by about 1/32 inch.
The spacing of the blades on the rotating shaft should be such that the peripheral speed of the rotating blade assembly is about the same as that of the ginning roller and, at the same time, permits the seed which still has fibers attached at the time of being released by the blade to be returned to the pinch point before being contacted by the next blade. The rotating blade assembly formed of the four spiral blades on the rotating shaft thus provides a plurality of channel-like pockets between the successive circumferentially spaced blades which are so correlated to the seed size and to the speed of rotation of the ginning roller and the rotating blade assembly as to cause the seed to be pushed away from the ginning point to a release position by engagement with the blade-like surface and then have time to return to the ginning point before the next blade-like surface moves to the ginning point.
It has been discovered that with such a small diameter rotating blade assembly or rotobar, it becomes difficult to obtain an even flow of cotton between the rotobar and the ginning roller. Obviously, if some of the cotton approaches the rotobar above the center line, it will be knocked back by the blades rather than being carried under the blade assembly to the zone of contact with the friction surface of the ginning roller. To alleviate this and achieve uniform feeding of the cotton to the ginning roller, a larger diameter auxiliary roller may be provided, spaced slightly upstream from the rotobar toward the discharge end of the feed chute, to press the cotton to the ginning roller and allow it to feed under the rotobar evenly.
An object of the present invention, therefore, is the provision of a novel roller gin construction having a rotating blade or rotobar device of small diameter and novel construction arranged immediately adjacent the working or leading end of the stationary knife, having an appropriate configuration and surface speed and spacing between blades to move the seed away from the knife edge and then allow it to return to the knife edge before the next blade hits the seed, and maintaining the surface speed relationship between the rotating blade assembly and the ginning roller so as to avoid an accumulation of unginned cotton on the ginning roller ahead of the rotating blade.
Another object of the present invention is the provision of a novel roller gin having a rotating blade device of small diameter relative to the diameter of the ginning roller having blades arranged in a spiral path spaced to define channel-like pockets therebetween so correlated to the seed size and to the speed of rotation of the ginning roller and the rotating blade device as to cause the seed to be pushed away from the pinch point of the working end of the stationary knife to the release point by engagement with the blade-like surfaces on the rotating blade device and then have time to return to the pinch point before the next blade-like surface moves to the pinch point, the release point being such that the seeds are not pushed out of the ginning zone with fibers still attached.
Yet another object of the present invention is the provision of a novel roller gin construction having a rotating blade device adjacent the edge of the stationary knife provided with plural blades transversely spanning the width of the gin and extending in a gentle spiral path, for example of about one turn, providing a blade device of small diameter compared to the diameter of the ginning roller having a surface speed close to the surface speed of the ginning roller, which prevents vibration, chattering or bumping of the rotating blade device when operating at higher capacity, arising from build-up of the seed and fiber against the knife edge in the interval between the passing of the rotating blades over the knife edge, and which substantially eliminates unginned seed locks being carried over with ginned seed.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating preferred embodiments of the invention.